Fluid control valve assemblies are used in a variety of fluid systems. For example, irrigation sprinkler systems commonly include a fluid control valve for controlling the supply of water under pressure to one or more irrigation sprinkler devices, which deliver the irrigation water to surrounding terrain and associated vegetation. Fluid control valves are intended to define a path permitting the flow of fluid along the flow line when the valve is opened, and to form a fluid-tight seal preventing the flow of fluid when the valve is closed.
Many conventional fluid control valves suffer from a significant pressure spike when the valve is closed and the fluid flow is abruptly stopped. The pressure spike is the resulting rapid rise in pressure above the static pressure of the source caused by water hammer. The shock wave caused by water hammer can be of sufficient magnitude to cause physical damage to piping, equipment, and, in severe cases, may present a safety hazard.
One valve design that significantly reduces the water hammer effect is the bladder-style valve. One version of the bladder-style valve is described in U.S. Pat. No. 5,632,465. Bladder-style valves include a hemispherical diaphragm that seals into a hemispherical portion of a valve chamber, thereby isolating the inlet from the outlet when the valve doses. The diaphragm gradually rolls over the inlet and the outlet as it closes so that the energy due to the motion of the fluid flow is essentially zero by the time the valve is closed. Consequently, water hammer is avoided. Bladder-style valve designs have an additional advantage over many conventional fluid control valves in that pressure loss is significantly lower, there are fewer parts in the design, which results in lower material cost, lower tooling cost, fewer assembly processes, and lower material logistics costs.
Current bladder-style valve designs have three drawbacks. The first drawback is that the diaphragm tends to be forced through the outlet aperture, especially at higher pressures. This abrades the diaphragm against the sharp aperture edges that result from molding the body of the valve. This forced abrasion results in significant scoring and cutting after only a relatively few cycles. The second drawback is that the entire system must be shut down to service the valve. The third is that air remains stuck in the bonnet even after the valve is run for some time. This air can result in undesirable valve-closing characteristics.
Thus, it would be desirable to provide a bladder-style valve that protects the diaphragm from abrasion and cutting, is easily serviced without shutting down the entire irrigation system, and is able to release all the air out of the bonnet to improve dosing characteristics.